Prince John's infantile behavior whenever someone mentions his mother is a sly reference to the real King John "The Fool" of England. The brother of King Richard "the Lionheart", John, the favorite son of their mother (Queen Eleanor of Aquitaine), was said to be crude and dim-witted, and attempted to usurp the throne from Richard while the latter fought in a crusade. Though Richard eventually returned from battle and foiled John's rebellion, John eventually became king anyway after Richard's untimely death (1199) in battle without an heir. Queen Eleanor supported John against rival claimants until her death in 1204.
A few months before the film's release, the Disney animators needed Peter Ustinov to come back to the Disney Studios to re-record some of his lines as Prince John. The animators made phone calls to New York, London, Paris, Vienna, and Tokyo, trying to locate Ustinov -- only to discover that he was working at the NBC Studios in Burbank that week, a half-mile down the street from them.
During the "Phony King of England" segment in the forest the illustrators referred to previous Disney films for inspiration. Maid Marian's dance movements are copied from both "Snow White" and "Duchess" (The AristoCats (1970)). The animals playing the various instruments are lifted almost verbatim from "The Aristocats." Also, the dance between Little John and Lady Cluck is lifted from the dance between Baloo and King Louie in The Jungle Book (1967).
The University of Southern California fight song, "Fight On," is played during the chase scene after the archery contest. "On Wisconsin," the fight song of the University of Wisconsin is also used during the "football" sequence of this scene.
A possible ending included Robin Hood being wounded, Prince John is about to stab him but is interrupted by King Richard. The filmmakers felt it made Prince John too sinister and was too dark so that particular ending was dropped. It is however included in the "Most Wanted Edition" DVD.
Initially, the studio considered a movie about the European fable, Reynard the Fox. However, due to Walt Disney's concern that Reynard was an unsuitable choice for a hero, Ken Anderson used many elements from it in Robin Hood. Particularly the animal counterparts (e.g. Robin Hood, like Reynard was a fox and The Sheriff, like Isengrin was a wolf.)
This film is noted for its frequent "recycling" of animation sequences. For example: the shot of the animals marching in the parade at the archery contest is identical to the shot of the same animals leading Prince John's carriage in the forest.
Tommy Steele was the original choice to perform the voice of the title character, but he was dropped shortly after recording sessions began. Terry Jones of "Monty Python" fame was also considered for the role.